Sewer line fails at Luther Burbank
Published 4:24 pm Monday, November 24, 2008
Heavy rains, cold temperatures and last month’s power outage have crippled or damaged portions of the Island’s water and sewage systems, bringing flurries of emergency construction to the Island.
After the storm on Dec. 14, a 40-year-old, county-owned sewer line near the Community Center at Mercer View cracked and burst, leaking untreated sewage into Luther Burbank Park and Lake Washington. The pipe failure caused the road to buckle. County officials closed the park’s shore for six days. Then, a concrete water pipe that connects the city’s water system to the main line from Seattle Public Utilities cracked and flooded a house in the 9000 block of S.E. 40th Street and the city maintenance shop last week.
What began as a few small sinkholes in the roadway has become a larger-than-expected, three-month, $6-to-7 million emergency construction project. Replacing the sewer line requires 2,300 feet of temporary, above-ground sewer pipe, street closures, pavement and vegetation removal, traffic detours, and habitat restoration.
In addition to the 1,800 feet of PVC pipe built two weeks ago outside the community center and along the side of Luther Burbank, construction crews laid more emergency pipe within the wetlands in the southern portion of the park last week. The extra 500 feet replaced pipe after county inspectors found more cracks in another segment of the sewer, said Monica Van Der Veiren, a spokesperson with the county’s wastewater division. The agency decided it was better to replace the entire line than return in a few years when the pipe reaches the end of its design life.
The most recently discovered cracks are underneath vegetation on a hillside above the wetlands surrounding the south parking lot of Luther Burbank. The wetlands will be damaged, but it is a public health emergency and the necessary permits are not required to be completed until after the construction.
To complete the transfer from the old pipes to the new bypass line, the North Mercer pump station was shut down three separate times. None of the transfers resulted in a sewage overflow, Van Der Vieren said, even though it was a possibility if the level of sewage exceeded the station’s capacity.
Van Der Vieren had more to worry about than overflows and the wetlands. Adjacent to wetlands is a private koi pond worth a couple million dollars. Van Der Vieren had to make sure construction noise and vibrations wouldn’t harm the fish.
To replace the old pipe, the county wastewater division has decided to use a method called pipe bursting because it eliminates the use of a trench and will minimize the damage to the wetlands. Crews from Frank Coluccio Construction will begin installing the new sewer line by the end of the month. Pipe bursting is a method that uses the existing pipe as a sleeve to position the new pipe as it is pulled through the line.
Van Der Vieren said the old pipe broke because of power surges at the pump station during the power outage. She said it wouldn’t have broken at normal pressures.
The section of road between the north and south entrances to Luther Burbank will remain closed to through traffic until construction is completed. A lane is expected to be closed in the north entrance and a 100-foot section of North Mercer Way will be closed soon. But Van Der Vieren said construction crews have already begun building a temporary roadway around the closure. The school district is going to test the road diversion with an empty bus to make sure buses will be able to use it. If the buses have difficulty, then the county will remove the curb to improve accessibility.
Van Der Vieren promises the county will restore the area to the conditions that existed before the storm. When the emergency construction is finished, the county plans to re-pave the streets, remove invasive plants like some of the blackberry bushes and plant natural vegetation as well as restoring the wetlands at Luther Burbank.
However, those restoration projects may not begin the day after construction crews leave, Van Der Vieren said. The county may try to work the street repairs into the city’s current street improvement plans and replant the removed trees later in the spring or summer.
“This has been a very important issue to the neighbors we have spoken with,” Van Der Vieren said. “And they’ve endured a lot of construction activity, love their park, and they want to know that we’ll return them to ‘good’ when we’re done.”
County officials have scheduled a community meeting on Feb. 3 from 10 a.m. to noon at the Community Center at Mercer View to present the project plans.
Water reserves used for several hours Jan. 11
When a major city water main operated by Seattle Public Utilities broke around 2:30 a.m. on Jan. 11, about 2,000 residents in the Shorewood Apartments were left without water for a day and the rest of the city was using reserves from the city’s two water tanks.
The water leaking from the broken pipe also flooded a nearby home in the 9000 block of S.E. 40th Street and the city maintenance shop located down the hill.
SPU supplied Shorewood residents with bottled water while they worked to fix the break, which was complete by 6 p.m.
A spokesperson for SPU doesn’t think a cause for the break will ever be determined, but the city’s newsletter reported that it may have been caused by shifting ground cracking a weld joint.
According to Terry Smith, a utilities operations manager with the city, Mercer Island personnel discovered the leak around 4 a.m. when they were sanding streets for snow and ice.
There is presently a four- to six-day water supply on hand in the tanks at Rotary Park near the library. The city is currently drilling in search of a larger emergency water source at the park.
